It is known to level this metal strip by a tension leveling process or in a tension leveling apparatus which has a brake roll set and a tension roll set. Both roll sets have as a rule two or more rolls which are looped by the strip.
For stretch leveling, a strip can be passed in such manner about two or more rolls which are operated with stepped torques or peripheral speeds so that between two rolls a stretching tension can be applied. Between the brake rolls sets and the tension roll sets, therefore, there can be a region in which the strip is subjected to tension, is stretched and is leveled.
In stretch leveling, there is a plastic elongation of the strip and a reduction of the strip thickness and strip widths. In prior systems, longitudinal stresses were produced and as a result of them, transverse stresses were created in the strip. As a consequence, greater longitudinal deformation could occur in the middle of the strip than would be present outwardly of the middle of the strip, resulting in residual stresses which were not uniform across the width of the strip.
To minimize the deformation which arose through stretch leveling and thus the central dishing of the strip and the nonuniform distribution of residual stresses therein, it has been proposed to provide between the braking roll set and the tensioning roll set a tension leveling roll path creating a stretching tension in the strip in the plastic range (see DE 39 122 676 C2).